Tohoku
J. exp.
Med.,
1977, 123,
393-394
Short Report A Secular Trend in Age at Menarche City and Its Surroundings
in Sendai
MASAKI MORIYAMA, HIROSHI KASHIWAZAKI, TAI-ICHIRO TAKEMOTO and TSUGUYOSHI SUZUKI
Department of Public Health, Tohoku University School of Medicine, Sendai 980
MORIYAMA,M., KASHIWAZAKI,H., TAKEMOTO,T. and SUZUKI, T. A Secular Trend in Age at Menarche in Sendai City and Its Surroundings. Tohoku J. exp. Med., 1977, 123 (4), 393-394 A secular trend in age at menarche was examined for 1,333 women living in Sendai city and its surroundings by applying the birth-year cohort analysis and the cross-sectional probit analysis. The trend toward younger menarcheal ages was consistently observed by both analyses, and it started off soon after the second World War. The speed was 0.11 year/year for the observation period of 1946 to 1966. age at menarche; sexual matura tion; secular trend in age at menarche The age at menarche has become earlier through over the period of a century (Tanner 1955) and now seems to be at the end of acceleration (Damon 1974) in several Western countries. In Japan, the trend toward earlier menarche in a certain period after the second World War has been noticed by some investigators (Matsumoto et al. 1963; Uno 1972), but the periods of observation in these reports were not adequately long to find when the trend started off and how was the speed of acceleration in sexual maturation. A chance to study age at menarche was available to us when a relatively large-scale enquete survey was conducted on the health of women working as teachers in primary and secondary schools or nurses in hospitals or day nurseries in the city of Sendai and its surroundings. Number of responses amounted to 1,333 (age of respondents: 18-52 years old). Of these 1,333 women, none menstruated before 10 years of age, and 3 women attained their menarche after 20 years of age. Mean and standard deviation of age at menarche were calculated for each birth-year cohort of women - 35 birth-year cohorts since 1924 to 1958 of varying sizes (11-92). In addition to calculation on the birth-year cohort, the probit analysis was applied to obtain the mean menarcheal age on each calendar year, when rates of menstruating in different age groups (10-20 years old) at the end of each calendar year were used for calculation. To make the trend in age at menarche clear, the method of moving averages using 7 consecutive values was applied for both sets of the mean menar cheal ages.
Thus, the results are shown in the figure, which shows a constant downward trend in age at menarche. The trend is conspicuously consistent between the two sets of results except that the recent mean ages are slightly younger in the probit analysis than in the birth-year cohort analysis. The downward trend started off soon after the second World War in the groups of women born in the middle of 1930's. The speed of acceleration is estimated at 0.11 year/year. The downward trend of menarcheal age began to stagnate in the women born after 1952. Interesting is The socio-economic Received
the release of the downward trend soon after the second World War. confusion during and after the second World War should have worsened
for publication,
June
14, 1977. 393
394
Fig.
M. Moriyama
1.
Secular
trend
Age
at
menarche
Age
at
menarche
Age
at
menarche
menarche figure
on are
in of on of
each
moving
age each each each
calendar averages
at
et al.
menarche.
birth
year
cohort: •ü,
calendar birth year by
mean;
year: •œ, year
cohort
is
plotted
7
consecutive
v,
the
latest;
n,
the
earliest.
mean.
at
is year
plotted of
at
year
observation.
of
birth, All
the
and
age
values
in
at the
values.
the nutritional status of adolescent girls at that time. Therefore, nutrition does not explain the secular trend, or at least the initiation nutrition, but what ? This is a question of further scrutiny.
the improvement of the trend.
in Not
Acknowledgments We appreciate M. Wada.
the collaboration
of Messrs.
J. Koizumi,
H. Minakami,
S. Uehara
and
References
1) 2) 3) 4)
Damon, A. (1974) Larger body size and earlier menarche; the end may be in sight . Soc. Biol., 21, 5-11. Matsumoto, S., Ozawa, M., Nogami, Y. & Ohashi, H . (1963) Menstrual cycle in puberty. Gumma J. med. Sci., 12, 119-143. Tanner, J.M. (1955) Growth at Adolescence. Blackwell Scientific Publications , O xford. Uno, R. (1972) Studies on the menarche , Part 1. Changes of the aspect of the menarche appearance. Kanazawa Daigaku Kyoikugakubu Kiyo . (Japanese)
J. exp.
Med.,
1977, 123,
393-394
Short Report A Secular Trend in Age at Menarche City and Its Surroundings
in Sendai
MASAKI MORIYAMA, HIROSHI KASHIWAZAKI, TAI-ICHIRO TAKEMOTO and TSUGUYOSHI SUZUKI
Department of Public Health, Tohoku University School of Medicine, Sendai 980
MORIYAMA,M., KASHIWAZAKI,H., TAKEMOTO,T. and SUZUKI, T. A Secular Trend in Age at Menarche in Sendai City and Its Surroundings. Tohoku J. exp. Med., 1977, 123 (4), 393-394 A secular trend in age at menarche was examined for 1,333 women living in Sendai city and its surroundings by applying the birth-year cohort analysis and the cross-sectional probit analysis. The trend toward younger menarcheal ages was consistently observed by both analyses, and it started off soon after the second World War. The speed was 0.11 year/year for the observation period of 1946 to 1966. age at menarche; sexual matura tion; secular trend in age at menarche The age at menarche has become earlier through over the period of a century (Tanner 1955) and now seems to be at the end of acceleration (Damon 1974) in several Western countries. In Japan, the trend toward earlier menarche in a certain period after the second World War has been noticed by some investigators (Matsumoto et al. 1963; Uno 1972), but the periods of observation in these reports were not adequately long to find when the trend started off and how was the speed of acceleration in sexual maturation. A chance to study age at menarche was available to us when a relatively large-scale enquete survey was conducted on the health of women working as teachers in primary and secondary schools or nurses in hospitals or day nurseries in the city of Sendai and its surroundings. Number of responses amounted to 1,333 (age of respondents: 18-52 years old). Of these 1,333 women, none menstruated before 10 years of age, and 3 women attained their menarche after 20 years of age. Mean and standard deviation of age at menarche were calculated for each birth-year cohort of women - 35 birth-year cohorts since 1924 to 1958 of varying sizes (11-92). In addition to calculation on the birth-year cohort, the probit analysis was applied to obtain the mean menarcheal age on each calendar year, when rates of menstruating in different age groups (10-20 years old) at the end of each calendar year were used for calculation. To make the trend in age at menarche clear, the method of moving averages using 7 consecutive values was applied for both sets of the mean menar cheal ages.
Thus, the results are shown in the figure, which shows a constant downward trend in age at menarche. The trend is conspicuously consistent between the two sets of results except that the recent mean ages are slightly younger in the probit analysis than in the birth-year cohort analysis. The downward trend started off soon after the second World War in the groups of women born in the middle of 1930's. The speed of acceleration is estimated at 0.11 year/year. The downward trend of menarcheal age began to stagnate in the women born after 1952. Interesting is The socio-economic Received
the release of the downward trend soon after the second World War. confusion during and after the second World War should have worsened
for publication,
June
14, 1977. 393
394
Fig.
M. Moriyama
1.
Secular
trend
Age
at
menarche
Age
at
menarche
Age
at
menarche
menarche figure
on are
in of on of
each
moving
age each each each
calendar averages
at
et al.
menarche.
birth
year
cohort: •ü,
calendar birth year by
mean;
year: •œ, year
cohort
is
plotted
7
consecutive
v,
the
latest;
n,
the
earliest.
mean.
at
is year
plotted of
at
year
observation.
of
birth, All
the
and
age
values
in
at the
values.
the nutritional status of adolescent girls at that time. Therefore, nutrition does not explain the secular trend, or at least the initiation nutrition, but what ? This is a question of further scrutiny.
the improvement of the trend.
in Not
Acknowledgments We appreciate M. Wada.
the collaboration
of Messrs.
J. Koizumi,
H. Minakami,
S. Uehara
and
References
1) 2) 3) 4)
Damon, A. (1974) Larger body size and earlier menarche; the end may be in sight . Soc. Biol., 21, 5-11. Matsumoto, S., Ozawa, M., Nogami, Y. & Ohashi, H . (1963) Menstrual cycle in puberty. Gumma J. med. Sci., 12, 119-143. Tanner, J.M. (1955) Growth at Adolescence. Blackwell Scientific Publications , O xford. Uno, R. (1972) Studies on the menarche , Part 1. Changes of the aspect of the menarche appearance. Kanazawa Daigaku Kyoikugakubu Kiyo . (Japanese)
